Commercially feasible and economical processes for the manufacture of substituted 1,1-difluoro(mono- or dihalo)ethoxybenzeneamines are desirable because these compounds are useful as intermediates in the preparation of valuable substances, such as agricultural herbicides and pesticides. Thus, substituted 1,1-difluoro(mono- or dihalo)ethoxybenzeneamines are employed as intermediates in the preparation of the corresponding acyl ureas which are useful as insecticides (see, for example, U.S. Pat. Nos. 3,761,486 and 4,468,405). Similarly, certain aryloxyphenoxypropionanilides, which are useful for the selective control of graminaceous weeds (see Ser. No. 730,353 filed May 2, 1985), are readily synthesized by employing these compounds as intermediates.
Substituted difluoro(mono- or dihalo)ethoxybenzeneamines are generally prepared by the reaction of 1,1-difluoro(mono- or dihalo)ethylenes with hydroxybenzeneamines in the presence of an alkali metal or alkaline earth metal hydroxide and in a polar, aprotic, water-miscible solvent as described, for example, in U.S. Pat. No. 3,926,898. The reactions proceed well and the desired products are formed in good yield. Isolation of the products from the reaction mixtures obtained, however, has proved to be difficult and the methods conventionally employed do not lend themselves to commercial operations. Thus, the isolation procedures described to date for recovering substituted 1,1-difluoro(mono- or dihalo)ethoxybenzeneamines prepared in this manner all involve dilution of the reaction mixture with water to insolubilize the product and subsequent separation of the product containing oil or solid phase that forms from the aqueous phase. Normally this is accomplished with the aid of another, water-immiscible solvent. Thus, in a typical procedure, the reaction mixture obtained is diluted with water and methylene chloride to obtain a biphasic liquid mixture. The two phases are separated and the methylene chloride phase is distilled to remove the methylene chloride, leaving the desired product in crude form as a residue. The crude substituted 1,1-difluoro(mono- or dihalo)ethoxybenzeneamine products thus obtained have been further purified by conventional means such as distillation and crystallization. Such isolation procedures have little value for commercial operations because the separation of the organic and aqueous phases present after the addition of water is very difficult, costly and time consuming, due to the formation of emulsions and the fact that both phases are very dark in color. Furthermore, the recovery and purification of the polar, aprotic, water-miscible solvent from the aqueous phase for recycle, which is important for commercial operations, is expensive and difficult. The recovery and purification of the optionally employed water-immiscible solvent for recycle further adds to the expense.
The isolation schemes defined hereinabove, which are currently employed for the isolation of substituted 1,1-difluoro(mono- or dihalo)ethoxybenzeneamines, were all designed to avoid further reactions of the products with the alkali metal or alkaline earth metal hydroxides present in the reaction media, which reduce the yields and additionally complicate the isolation of the products. The further, deleterious reactions known to take place include dehydrofluorination, hydrolysis, and conversion to orthoformate esters. These reactions are analogous to the degradative reactions of alkyl 1,1-difluoro(mono- or dihalo)ethyl ethers discussed in J. Am. Chem. Soc. 73, 1781(1951). The known isolation schemes avoid such reactions by physically separating the alkali metal or alkaline earth metal hydroxides from the desired products by virtue of the solubility of such hydroxides and insolubility of the products in aqueous media.